Turbochargers for internal combustion engines can include a wastegate for controlling the portion of the exhaust stream that is directed through the exhaust gas turbine stage of the turbocharger. By varying the position of the wastegate, the level of boost provided by the compressor stage of the turbocharger can be increased or decreased accordingly. Engines including twin turbochargers, such as V-engines, can utilize wastegate control to balance the level of boost provided by each of the turbochargers. Typically, for twin turbocharged engines, it is assumed that the system is symmetric, and as such each wastegate is concurrently commanded to the same position.
However, the inventors herein have recognized that most V-engine systems are not completely symmetric. Asymmetries present in V-engine systems may include differences in exhaust system routing, exhaust manifold design, turbine housing casting design, and/or wastegate passage design between the banks of the engine. Additionally, manufacturing variability may introduce asymmetry into the wastegate passages or spring system used to oppose the pneumatic force in pneumatically-actuated wastegates. Further, hysteresis within the actuators may cause asymmetry, where small movements may result in each actuator being at opposite ends of the hysteresis band.
Thus, even if the wastegates are commanded to the same position, imbalance between the turbochargers may still result due to the asymmetry present in the system. This may result in the turbochargers operating in different operating states, such as operating with different turbine power, turbine shaft speed, and for pneumatic actuators, different wastegate position. Under some engine operating conditions, it may be desirable to operate near the turbine shaft speed limit. However, in an asymmetric system, the fastest rotating turbine will limit the performance of the system, and depending on the magnitude of the asymmetry, the capability of the system may be greatly reduced.
Accordingly, an engine system is provided which may allow for detection and balancing of asymmetries present in a V-engine with two turbochargers. The engine system comprises a first turbocharger including a first wastegate, first wastegate actuator, and first turbocharger sensor, a second turbocharger including a second wastegate, second wastegate actuator, and second turbocharger sensor, and a controller configured to adjust the first wastegate actuator so that a parameter of the first turbocharger matches a parameter of the second turbocharger, based on output from the first and second turbocharger sensors.
In this way, output from turbocharger sensors may be used to detect if a turbocharger parameter, such as turbine speed or power, is out of balance between the two turbochargers. If the turbochargers are out of balance, the wastegate of at least the first turbocharger may be adjusted until the turbocharger parameters are brought into alignment. In this way, small variations in the amount of boost provided by each turbocharger may be balanced. Further, engine performance may be increased by detecting if a turbocharger is operating at a speed or power output lower than desired, and adjusting the wastegate of that turbocharger to increase the turbocharger performance.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.